Method of drawing fibrous thermoplastic sheet material



P. R. ZINSER Nov. 30, 1937.

METHOD OF DRAWING FI BROUS THERMOPLASTIC SHEETMATERIAL Filed Feb. 19, 1936 I INVENTOR. I Paw/f5. Z/hser BY Fa/zm/z/ $5M ATTORNEY.

Patented Nov. 30, 1937 UNITED STATES METHOD OF DRAWING FIBROUS THERMO- PLASTIC SHEET MATERIAL Paul R. Zinser, Detroit, Mich., assignor to Woodall Industries, Incorporated, Detroit, Mich., a corporation of Michigan Application February 19, 1936, Serial No. 64,632

)7 Claims.

result and to the drawing of material which possesses little capacity for stretch. An example of such .a material is composition fiber board formed of a multiplicity of relatively short cellulose fibers held together by a suitable thermoplastic binder such as an asphalt composition.

This type of material is capable of being shaped under pressure in a heated die into various forms. A common use of such material is in the fabrication of panels such as here employed in the interiar of closed automobile bodies. These panels are decoratively embossed, being provided with beads and other decorative designs. The material readily responds to this heat and pressure treatment to assume and permanently retain a deformed shape. It is frequently desired to give the sheet of material a deeply drawn deformed shape wherein the draw is of such a depth that the material is stretched or drawn beyond its safety limit and rupture or breakage of the sheet is the result. One practice which has been followed to facilitate such deep drawing is to subject the sheet to two operations. In the first operation the sheet of material is given a deep draw contour. In the second operation the sheet is subjected to the same dies but the dies are heated to a higher temperature and the asphaltum or other thermoplastic binder is fused and caused to fiow so as to seal up any breaks or cracks which may have resulted from the first operation. While this improves the appearance and also the structure of the sheet it does not weld the sheet together along the line of breakage throughout its interior in such manner as to give it the strength it once possessed and as a consequence the sheet issubstantially weakened by this drawing operation.

An object of this invention is to subject a sheet of the desired material to' a preliminary deforming operation which facilitates its deep drawing. In the preliminary operation here shown the sheet is subjected to what might be termed a corrugating treatment whereby a succession of relatively small deformations or corrugations are progressively imparted to the sheet without appreciably stretching the structure thereof and in this form the sheet is subjected to the deep drawing operation. Material necessary for the draw is obtained PATENT OFFICE.

from the flattening out of the deformations. The deep draw therefore is accomplished with a minimum of stretch of the sheet and aminimum strain imposed thereon and the drawn sheet'is not weakened appreciably by the drawing operation.

' Specifically, my improvement consists in deforming a fiat sheet by successively corrugating the same in such a manner that the material is given the corrugated shape without any undesirable weakening of the material. In the corrugating operation illustrated the sheet'is corrugated through progressively forming individual corrugations therein without undesirablestretch ing of the material at any point. The jcorrugated portion of the sheet is then subjected to the drawing operation and the material necessary for the 'draw is taken up from what might be termed the slack of the folds or corrugations Without stretching the material of the sheet.

Other objects, advantages, and meritorious characteristics of my invention'will more fully appear from the following description, appended claims, and accompanying drawing, wherein:

Figure v1 is a diagrammatic illustration of the first step in my improved process, I Fig. 2 is a fragmentary plan of a sheet 0 material'following the first step in my improved.

process,

Fig. 3 is an elevation of a fragment of a press disposed to carry out one of the steps in myimproved process,

Fig. 4 is an elevation of the fragment of the press shown in Fig. 3 in the operative position, and

Fig. 5 is aperspective of a panelfabricated a'ccording to my improved process.

In the primary step of corrugating the sheet preparatory to the drawing thereof such corrugation'is accomplished without appreciably stretching the sheet or undue tension tending to separate the fibers. For example, a sheet 36" long before being passed through the corrugating rolls might have a length of only 32" after being passed therethrough. The depth of the corrugations, however, would depend upon the depth of the draw towhich the sheet is to be subjected. It

is apparent thata corrugation of one depth would point. The sheet might be corrugated only through a portion of its area, the extent of such corrugated area being determined by the extent of the deformed area desired in the final product.

In the drawing I have illustrated a sheet of suitable fibrous composition thermoplastic material l such as hereinabove described. This sheet is pressed between corrugating rolls I 2; The sheet may be subjected to a steam heating operation prior to being passed therethrough to soften the binder and render the fibers pliable and the rolls may be heated to the temperature.

best suited to accomplish the corrugating of the sheet. Material which is suitable for this use is on the market under the name of K Bboard.

This material is formed of cellulose fibers held together by a composition asphaltum binder. It is responsive to heat and pressure to assume and permanently retain a deformed shape. A sheet of this material is passed between' the corrugating rolls I2 as diagrammatically illustrated herein; After being passedbetween such rolls it possesses the shape shown in Figs. 2 and 3.

The sheet so shaped is then pressed in a suitable press such as indicated in Figs. 3 and 4 and subjected to the required stamping operation of a hot die l I andforce 13 to give to it the desired final shape, as shown in Fig. 5. The sheet of materialmay be preheated before the die stamping' operation to facilitate its shaping. A conventional deep draw is shown in Fig. 5 wherein the sheet is shaped as appears in certain dash panel formations now being. used, and given a deep drawcontour as at M.

With the sheet corrugated in one direction only the flatteningout of the corrugations facilitates the draw in one direction better than it does in the other but the corrugated character of the sheet is such that the material flows under the pressure of the die from where there is an excess of material to where material is needed. Due to this flow of material the sheet is built up in one place and thinned out in another as the requirements of the draw demand. There is such an excess of material in the folds or corrugations as to cause material" to flowtherefrom to the place where it is needed.-

In a sheet so prepared it will be found that the excess of material in the corrugations is suflicient to permit the material to fiow so that the sheet will assume the desired deep draw contour without undue strain or tension being placed on the sheet at any point and without breakage or rupture of the sheet as a result of such drawing. When the drawing of the sheet is carried out according to this disclosure the gauge or thick ness of the material therein will not be appreciably different followingthe drawing from what it was preceding the drawing.

In the deepdrawing operation the corrugations may be completely ironed out through the entire areaof the sheet or only partially ironed out making a corduroy type. of appearance. The corrugations may be ironed out through that portionof the sheet which is deeply drawn and left in other portions of thesheet which are not subjected to the deepdrawingoperation serving to stiffen or strengthen such other portions.

What I claim is:

1. That method of imparting a permanently deformed shape to a sheet of composition fibrous thermoplastic material which includes the preparatory step of subjecting the sheet to an operation which imparts progressively and successively a multiplicity of relatively small deformations thereto without appreciable stretching of the sheet'and thereafter shaping'saidcorrugated portion of the sheet flattening out said corrugations.

2. That method of imparting a permanently deformed shape to asheet of composition fibrous thermoplastic material which comprises subjecting the sheet to a forming operation which imparts a multiplicity of relatively small deformations-tliereto and thereafter drawing the sheet to a permanently deformed shape through the flattening out of saidplurality of relatively small deformations during said drawing operation.

3. That'method of imparting a permanently deformed shape to asheet of composition fibrous thermoplastic material which comprises subjecting the sheet to a forming operation which imparts a multiplicity of relatively smalldeformations thereto and thereafter drawing the sheet to a permanently deformed shape through the flattening out of said plurality of relatively small deformations throughout that portionwhich' is drawn to the permanently deformed shape and smoothing out said plurality of relativelyxsmall deformationsuponone face of said drawn portion.

4. That method of deforming a'sheet of composition material made up of a plurality of relatively short cellulose fibers held together by an asphaltum binder which includes the preparatory step of corrugatingthat portion of the sheet which is to be so deformed by progressively rolling successive corrugations into the sheet prior to the deforming, operation and thereafter deforming said corrugated portion.

5. That method of drawing a sheet of composition fibrous. thermoplastic material which includes the preparatory step of corrugating the sheet from one edge to the opposite edge" by progressively individually forming a succession of corrugations therein and thereafter drawing the corrugated sheet'to a-deformed shape. by fiattem'ng out said corrugations.

6. That method of imparting. a permanently deformed shape to a sheet of composition fibrous to progressively form a succession of corrugations therein, and thereafter stamping the corrugated portion of the sheet to a deformedshape'.

PAUL R. ZINSER. 

